Bromine-containing chemicals

The demand for bromine-containing chemicals for different sectors has strongly shifted in recent years, partly due to environmental considerations. This is demonstrated by the evolution in the application spectrum for bromine consumption in the USA in the period 1980 to 1993 shown in Table 1.7-24. 

Scientists have also implicated some bromine-containing chemicals in the destruction of the ozone layer. The chief culprit has been CHjBr, methyl bromide, a commonly used agricultural fumigant. Here again, it is the relatively weak G—Br bond that is broken by UV radiation to produce Br atoms, which act in the same role as Cl atoms to destroy ozone. 

An important use of bromine compounds is in the production of flame retardants (qv). These are of the additive-type, which is physically blended into polymers, and the reactive-type, which chemically reacts during the formation of the polymer. Bromine compounds are also used in fire extinguishers. Brominated polymers are used in flame retardant appHcations and bromine-containing epoxy sealants are used in semiconductor devices (see... 

Flame Retardants. Bromine compounds make up an important segment of the market for flame retardants used in polymers. Additive flame retardants are added to polymers during processing reactive flame retardants react chemically to become part of the polymer chain itself. In addition to the compounds Hsted in Table 3, a number of proprietary mixtures and phosphoms—bromine-containing flame retardants are also sold (see Elame RETARDANTS, HALOGENATED, FLAAffi RETARDANTS). 

In spite of the fact that biotechnology rather than chemical processing will probably provide the future greatly needed chirally pure compounds (ref. 1), we believe that simple chemical reactions starting from chiral natural compounds and proceeding under stereochemical control will eventually retain full importance. On the above grounds, we report on simple reactions which start from a-aminoacids, as an example of utilization of natural compounds, and move to related bromine containing compounds (Fig. 1). 

Bromine is applied to flame retarding (FR) polymers in a number of systems, which are divided into two major groups, according to the way in which the FR agent interacts with the polymer [1). In one group, e.g. the reactive systems, the bromine is chemically bound with the polymer. The introduction of the bromine into the polymer molecule can be carried out by copolymerizing a bromine-containing... 

A review is presented on European regulatory initiatives focussing on products containing chemicals, which are potential sources of environmentally hazardous materials. Particular attention is paid to brominated flame retardants in the light of the European Commission s official position in relation to the Precautionary Principle. 18 refs. EUROPEAN COMMISSION... 

Generally, flame retardants for engineering PET compositions are based on bromine-containing compounds (such as brominated polycarbonate, decabro-modiphenyl oxide, brominated acrylic, brominated polystyrene, etc.). Such compounds are available commercially (such as from the Ethyl Chemical Corporation, Great Lakes Chemical Corporation, Dead Sea Bromine Company, etc.) In addition, the flame-retardant package generally contains a synergist, typically sodium antimonate. PET may also be flame-retarded with diarylphosphonate, melamine cyanurate or red phosphorus. 

The ionically bonded sodium bromide receives two electrons, and loses two +ve sodium cations to form sodium tri-bromide (see Porterfield, 1993). An alternative homogeneous reaction route to tri-bromide is to bubble bromine (Br2) through aqueous sodium bromide. Accordingly, the electrochemically formed tri-bromide has an associated atmosphere of bromine from homogeneous dissociation. Such bromine is corrosive, but is contained by the fluorinated plastic tanks and by one side of the (Na ) Nafion perm-selective membrane. Nafion is itself a compound with many fluorine atoms. Bromine is very much lower than fluorine in chemical reactivity, so that the bromine containment strategy is complete, and the selection of the bromide electrolyte seen to be a well-considered choice. 

Oxidizer Chemical substance that causes oxygen to combine with another chemical substance examples include oxygen and hydrogen peroxide Ozone depletion Destruction of the stratospheric ozone layer that protects the Earth from harmful effects of ultraviolet radiation. Depletion of ozone layer is due to the breakdown of certain chlorine- and/or bromine-containing compounds (chlorofluorocarbons or halons), which break down when they reach the stratosphere and then catalytically destroy ozone molecules Ozone layer Protective layer in the atmosphere, about 15 miles above the ground. The ozone layer absorbs some of the sun s ultraviolet rays, thereby reducing the amount of potentially harmful radiation that reaches the Earth s surface PAHs Polycyclic aromatic hydrocarbons... 

Bromine is used in silver bromide—based photographic films. It is also used to make NaBr and KBr, two chemicals used in sedatives and soporifics (sleeping aids). Bromine-containing compounds are also used as flame retardants for cloth (see Section 22.5). 

DOVER CHEMICAL CORP. Bromine Containing Flame Retardants ... 

The tables shown below illustrate the chemical shifts of a selected variety of bromine containing organic compounds. 

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